1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to an apparatus and method for driving a liquid crystal display device that selectively changes frame rate control (FRC) dithering patterns based on characteristics of an input image data to improve picture quality.
2. Discussion of the Related Art
Flat panel displays include a liquid crystal display, a field emission display, a plasma display panel, a light emitting display, and the like. The liquid crystal display, among the flat panel displays, displays an image by adjusting the light transmittance of a liquid crystal using an electric field.
Further, the liquid crystal display includes a liquid crystal panel having a plurality of pixels, a backlight unit for irradiating light to the liquid crystal panel, and a driving circuit for driving the pixels. The liquid crystal panel also includes a plurality of gate lines and a plurality of data lines arranged to intersect each other, and the pixels are located respectively in areas defined by the intersections of the gate lines and the data lines.
A pixel electrode and a common electrode for applying an electric field are also formed in each of the pixels. Further, the pixel electrode is connected with a thin film transistor (TFT), which is a switching element. The TFT is turned on by a scan pulse from each gate line to charge a data signal from each data line in the pixel electrode.
In addition, the driving circuit includes a gate driver for driving the gate lines, a data driver for driving the data lines, a timing controller for supplying control signals for controlling the gate driver and data driver, and a power supply for supplying driving voltages used to drive the liquid crystal panel and the respective drivers.
The liquid crystal display uses a frame rate control (FRC) dithering method to increase the number of gray scales of an image to be displayed. In more detail, the FRC dithering method is used to partition pixels into dither blocks each having a certain size to adjust the brightness of pixels in each block, and to make the brightness of the pixels in each block different for every frame so as to display a larger number of gray scales rather than a set one.
For example, when the FRC dithering method is used in a liquid crystal display where one pixel can display an 18-bit color with a combination of R, G and B data, it is possible to obtain a similar effect to displaying a 24-bit color with a combination of R, G and B data, each R, G and B data being 8 bits long. Thus, the liquid crystal display input R, G and B data of 18 bits can be displayed as a number of gray scales corresponding to R, G and B data of 24 bits.
However, the related art FRC dithering method is disadvantageous because it is used in the same manner irrespective of an inversion mode of a liquid crystal display or characteristics of an image being displayed on the liquid crystal display, resulting in a degradation in picture quality. In other words, when a liquid crystal display is driven in a dot inversion mode and displays an image having a certain horizontal or vertical pattern, a flicker may occur in which pixels at specific positions seem to shine.
Thus, because the related art FRC dithering method is used in the same manner irrespective of an inversion mode or characteristics of an image, a flicker, noise, dark bar or the like may occur in a specific pattern such as a dot pattern or horizontal/vertical striped pattern, causing a degradation in picture quality.